The short answer is Skin Studio. However the question , in and of itself, has a multitude of responses.

Yes neone6 and gmc2 are correct. The only way to have singular colours is by designing your own via Skin Studio. You could just open the image and re-colour using Hue/Saturation layer style save and apply

you need to download skinstudio from here:

https://www.stardock.com/products/skinstudio/downloads.asp

you should go here and read this, its an indepth tutorial for beginners, and it covers perpixel buttons and uis2 buttons,

https://forums.wincustomize.com/383387

alright i suggest you want to change perpixel buttons of the windowframes
It looks like you started a new skin ! since the screenshot shows skinname ...
close skinstudio and reopen it choose the skin that you want edit or modify and click open
then navigate to :
Edit Titlebars and Windowframes and then on the right you clickEdit per pixel buttons ...cheers

Yyy, wtf ? Ok, i am editing buttons, and applied, i have classic windows oO why ?

A few questions spring to mind.

1. Is Windowblinds correctly activated ?

2. What graphics card do you have ?

3. Have you posted a configuration report ?

If not you can post a report by opening the windowblinds configuration panel

 i. Clicking About Windowblinds on the top bar

 ii. Click copy to clipboard in the lower right corner of this dialog

 iii. Pasting it here in between [ code ] [ /code ] tags.